The molecular basis for the generation of action potentials or as it were the changes of electrical properties of the plasma membranes of animal cells in response to stimulation have great theoretical and practical significance. What kind of molecules in the membrane are involved in the control of voltage dependent sodium conductances? In order to gain an answer to this question one must first have accurate measurements of the time and voltage dependence of the membrane conductances to the pertinent ions, and second, one must also have the possibility of identifying and analyzing the molecular components of the membrane which give rise to the conductance changes. The enriched plasma membrane preparation will be obtained by 1) mildly homogenizing washed ventricles, 2) separating away the cellular debris by low speed centrifugation, 3) separating the plasma membrane fraction from other membranous components by centrifugation to equilibrium in various sucrose gradients. We will use modifications of the Weber Osborn SDS acrylamide gel system to separate and identify some 40 polypeptide constituents of various FCPM preparations using Coomassie Blue staining. We will use both cylindrical and slab gels. Earlier we have found of these some 15 bands are stained by PAS techniques and presumably at least these are glycoprotein. We have found that the polypeptides of this preparation are hard to dissolve and tend to aggregate. We will solubilize the proteins of the FCPM using 0.5 mM EDTA alone which we have found will solubilize around 50% of the plasma protein. We will separate and identify various solubilized proteins in detergent free gels.